1. Field of the Invention
The present invention relates to an electric motor.
2. Description of the Related Art
Some known motors of disk drive apparatuses include bearing mechanisms using fluid dynamic pressure. A spindle motor disclosed in JP-A 2009-136143 includes a shaft, a first bearing component, a second bearing component, and a rotor component. The first bearing component is arranged in the shape of a cup, and includes an opening portion arranged to pass therethrough in an axial direction in a center thereof. A lower portion of the shaft is fitted in the opening portion of the first bearing component. The second bearing component is annular, and is defined integrally with the shaft at an upper end portion of the shaft. The rotor component is arranged in a middle space defined by the shaft, the first bearing component, and the second bearing component. A fluid dynamic pressure radial bearing portion is defined between a cylindrical surface of the rotor component and an outer circumferential surface of the shaft.
A fluid dynamic pressure thrust bearing portion is defined between a lower surface of the rotor component and a surface of the first bearing component which is axially opposed to the lower surface. A seal gap which extends upward is defined outside the fluid dynamic pressure thrust bearing portion. A pumping seal portion is defined between a lower surface of the second bearing component and a surface of the rotor component which is opposed to the lower surface. Another seal gap arranged to extend upward is defined outside the pumping seal portion.
In recent years, additional reductions in thickness and size have been demanded of disk drive apparatuses. In particular, in order to achieve an additional reduction in the thickness of a drive apparatus including a 2.5″ disk, which is among small-sized disk drive apparatuses, it is necessary to reduce the thickness of a motor itself arranged inside a housing. A reduction in the thickness of the motor itself leads to a reduction in the axial dimension of a region over which different components are joined to each other. A reduction in the axial dimension of the region over which the different components are joined to each other may result in a reduction in strength with which the components are joined to each other, and the joint portion may be ruined as a result of a load or weight being imposed on the motor.